Law enforcement agents uncovered fields of marijuana plants in east-central Minnesota worth $4.1 million during one of state’s biggest drug busts in years.

Busloads of agents seized more than 5,500 marijuana plants Wednesday in a predawn raid of land east of Hinckley, according to the Drug Enforcement Administration.

“The focus of today’s effort was to locate, document and destroy these plants before they could be harvested and enter the illicit drug market,” Minnesota U.S. Attorney B. Todd Jones said in a statement. Officers from local, state and federal agencies executed the federal search warrant.

A helicopter flew overhead as agents secured a large perimeter and descended upon their target, according to a Pine City radio reporter who attended a preraid strategy session by authorities and witnessed the seizure.

“They never found any suspects,” said Jesse Logan, who reports for Red Rock Radio.

A DEA spokesman declined to answer questions about whether there are suspects, who owns the land and how long authorities had their eye on the operation.

In recent years, law enforcement agencies have reported busting multimillion indoor operations in the Twin Cities suburbs, calling them “pot palaces.” But news of outdoor operations is less frequent.

In July 1991, officials from the Bureau of Criminal Apprehension raided farms in north-central Minnesota and destroyed about 5,000 marijuana plants, then valued about $12.5 million. The raid was called among the largest in Minnesota’s history. Five men from Ohio were indicted on charges of cloning the plants in Ohio and growing them in Minnesota.

During Wednesday’s raid, Logan said school buses brought three teams of officers to the area. They walked for some time before coming upon the many thousands of plants, he said.

“There was one large swath of marijuana and several smaller ones nearby,” he said.

Officers were told during the briefing to anticipate finding about 10,000 plants in the ground with a street value of up to $7 million, Logan said. He added that officials at the briefing said they suspected up to six Mexican nationals were involved in the growing operation.

Amid the plants were at least two encampments, neither of them occupied at the time of the raid. Along with small tents and a tarp for shelter at one of the campsites, there was a gas stove and a makeshift table, Logan said. Also at the site was what appeared to be a rudimentary irrigation system, with pumps and hoses, he added.

“It doesn’t surprise me” that people were growing marijuana in the woods, said Davis, 53, who has lived in her lakeside home since 1991. She’s also not surprised she didn’t catch wind of it. It’s pretty rural, she said, with lots of trees.

“There are all kinds of people who are dealing drugs” in the area, Davis said. “I never heard of anybody growing any.”

Agencies involved in the raid included the Pine County Sheriff’s Office and the East Central Drug and Violent Offender Task Force, which includes personnel from Isanti, Pine and Chisago counties.